The proposed work investigates several major determinants of alcohol effects on aggressive an social behavior. Two major possible mechanisms for these alcohol effects are explored, alcohol's interaction with gonadal steroid hormones and with benzodiazepine receptors. Specifically, we plan to manipulate critical behavioral experiences that will modulate testosterone activity and thereby alter the sensitivity to behavioral effects of alcohol. We will investigate how time- and dose- dependent effects of alcohol on aggressive and social behavior are modulated by endogeneously varying or experimentally manipulated testosterone activity. Pre- and postnatal presence of differential amounts of testosterone in females are expected to modulate alcohol effects on aggressive and reproductive behavior in adulthood. Seasonal rhythms in gonadal hormone levels are expected to be associated with distinctive patterns of alcohol effects on aggressive behavior. Past experiences with aggressive or submissive behavior produce divergent changes in gonadal activity, and these changes are expected to alter certain behavioral effects of alcohol. In a second set of experiments the role of benzodiazepine receptors in the behavioral effects of alcohol will be investigated. Direct measurements of benzodiazepine receptor binding, concentration of benzodiazepines and metabolites in blood and brain, and pharmacological of benzodiazepine receptors with agonists, inverse agonists and antagonists will give information on the patential significance of these receptors in the effects of alcohol on aggressive, defensive, social, reproductive and motoric activities. The use of quantitative ethological methods for the recording and analysis of social and agonistic as well as automated measuremenmts of motor functions and startle responses will ensure assessment of behavioral specificity of the pharmacological treatments. This research will further our understanding of how alcohol exerts its effects on aggressive behavior and the ways in which gonadal hormones and benzodiazepines can modulate those effects.